<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>ID选择器</title>
    <style>
        #one {
            color: seagreen;
        }
    </style>
</head>
<body>
    <div id="one">div标签1</div>
    <div>div标签2</div>
    <div>div标签3</div>
</body>
</html>